First of all, I hope that I'm allowed to ask for some debugging help here. With that said, I've created this simple little tic tac toe program, and it basically is done, but this semantic error has been killing me.
Obviously, I've spent some time trying to figure out the problem on my own, but you could say that I've given up on that so here I am now :)
For some brief overview, the board is represented by an array of type char ttt[3][3]. Players are also variables of type char, so they are either 'X' or 'O' and the coordinates of the board are entered as letters:
A sample run will look like this:
********************************
---a------b------c---
| | | |
---d------e------f---
| | | |
---g------h------i---
| | | |
---------------------
player1: O, it is your turn.
Select a cell [a, b, c, ... i]
a
********************************
---a------b------c---
| O | | |
---d------e------f---
| | | |
---g------h------i---
| | | |
---------------------
player2: X, it is your turn.
Select a cell [a, b, c, ... i]
The array ttt[3][3] is initialized such that every element is just ' '.
For the most part, the program runs fine. To try to save some time for you guys, I'm confident that the following methods are running perfectly
- boolean winner(char player)
- boolean gameIsDraw()
- void displayBoard()
- String playerID(char player)
- and the main method
Where I do see a problem is most likely contained within my getPlayerInput(char player) method:
void getPlayerInput(char player)
{
int row = 0;
int col = 0;
System.out.println(playerID(player) + ", it is your turn.");
System.out.println("Select a cell [a, b, c, ... i]");
char answer;
answer = scan.next().charAt(0);
switch(answer)
{
case 'a':
row = 0;
col = 0;
break;
case 'b':
row = 0;
col = 1;
break;
case 'c':
row = 0;
col = 2;
break;
case 'd':
row = 1;
col = 0;
break;
case 'e':
row = 1;
col = 1;
break;
case 'f':
row = 1;
col = 2;
break;
case 'g':
row = 2;
col = 0;
break;
case 'h':
row = 2;
col = 1;
break;
case 'i':
row = 2;
col = 2;
break;
default:
System.out.println("Invalid location, try again.");
getPlayerInput(player);
}
if(ttt[row][col] != ' ')
{
System.out.println("This square is taken. Try again.");
getPlayerInput(player);
}
else
{
ttt[row][col] = player;
}
}
To me, it looks fine, but my output indicates otherwise. The method includes two failsafes,
if the user inputs something outside of the board range (chars outside of 'a' through 'i'),
or if the user selects a letter/location on the board that is already taken up by another 'X' or 'O'.
In both cases, the method prints out that some faulty input was entered and then calls getPlayerInput() again.
What I have come to notice via debugging is that if only valid inputs are entered in, the program seems to run fine. However, if a faulty input is entered (either type) and then a valid input is entered, sometimes the method will print that a faulty input was still entered.
For example,
********************************
---a------b------c---
| | | |
---d------e------f---
| | | |
---g------h------i---
| | | |
---------------------
player1: O, it is your turn.
Select a cell [a, b, c, ... i]
a
********************************
---a------b------c---
| O | | |
---d------e------f---
| | | |
---g------h------i---
| | | |
---------------------
player2: X, it is your turn.
Select a cell [a, b, c, ... i]
z
Invalid location, try again.
player2: X, it is your turn.
Select a cell [a, b, c, ... i]
e
This square is taken. Try again.
player2: X, it is your turn.
Select a cell [a, b, c, ... i]
f
********************************
---a------b------c---
| O | | |
---d------e------f---
| | X | X |
---g------h------i---
| | | |
---------------------
player1: O, it is your turn.
Select a cell [a, b, c, ... i]
Notice that I entered the char's a-z-e-f. 'z' obviously is an invalid character, so the method worked as intended (so far), printed that it was invalid input, then the method ran again, asking for input. 'e' was then entered, obviously a valid location, but the method printed that the "square was already taken" when it obviously wasn't. But, entering in a different char 'f' allowed to me exit it.
The end result is that player 'X' got two turns and filled both squares 'e' and 'f'.
It should be noted that if a user continually enters in bad input, that he should be stuck in that method until a valid input is entered, but this is clearly a case where good input is somehow misinterpreted as bad input, and the loop can't be exited unless a different instance of good input is entered in.
So, with all of that said, help meee?? Regardless, I highly appreciate anyone who's had the patience to read this far...
Should you like to run the code yourself, here is the source:
import java.util.*;
class TicTacToe
{
char ttt[][] = new char[3][3];
static final char player1 = 'O';
static final char player2 = 'X';
Scanner scan =new Scanner(System.in);
String playerID(char player)
{
if (player == player1)
return "player1: "+player;
else
return "player2: "+ player;
}
void getPlayerInput(char player)
{
int row = 0;
int col = 0;
System.out.println(playerID(player) + ", it is your turn.");
System.out.println("Select a cell [a, b, c, ... i]");
char answer;
answer = scan.next().charAt(0);
switch(answer)
{
case 'a':
row = 0;
col = 0;
break;
case 'b':
row = 0;
col = 1;
break;
case 'c':
row = 0;
col = 2;
break;
case 'd':
row = 1;
col = 0;
break;
case 'e':
row = 1;
col = 1;
break;
case 'f':
row = 1;
col = 2;
break;
case 'g':
row = 2;
col = 0;
break;
case 'h':
row = 2;
col = 1;
break;
case 'i':
row = 2;
col = 2;
break;
default:
System.out.println("Invalid location, try again.");
getPlayerInput(player);
}
if(ttt[row][col] != ' ')
{
System.out.println("This square is taken. Try again.");
getPlayerInput(player);
}
else
{
ttt[row][col] = player;
}
}
boolean gameIsDraw()
{
boolean isDraw = true;
for(int i = 0; i < 3; i++)
{
for(int j = 0; j < 3; j++)
{
if(ttt[i][j] == ' ')
{
isDraw = false;
}
}
}
return isDraw;
}
boolean winner(char player)
{
boolean hasWon = false;
// possible horizontal wins
for(int i = 0; i < 3; i++)
{
if(ttt[i][0] == player && ttt[i][1] == player && ttt[i][2] == player)
{
hasWon = true;
}
}
// possible vertical wins
for(int i = 0; i < 3; i++)
{
if(ttt[0][i] == player && ttt[1][i] == player && ttt[2][i] == player)
{
hasWon = true;
}
}
// one diagonal win
if(ttt[0][0] == player && ttt[1][1] == player && ttt[2][2] == player)
{
hasWon = true;
}
// other diagonal win
if(ttt[0][2] == player && ttt[1][1] == player && ttt[2][0] == player)
{
hasWon = true;
}
return hasWon;
}
void displayBoard()
{
System.out.println("********************************");
System.out.println(" ---a------b------c---");
for (int i=0; i<3; i++)
{
for (int j=0; j< 3; j++)
{
if (j == 0) System.out.print(" | ");
System.out.print(ttt[i][j]);
if (j < 2) System.out.print( " | ");
if (j==2) System.out.print(" |");
}
System.out.println();
switch (i)
{
case 0:
System.out.println(" ---d------e------f---");
break;
case 1:
System.out.println(" ---g------h------i---");
break;
case 2:
System.out.println(" ---------------------");
break;
}
}
}
void newgame()
{
char currPlayer = player1;
for(int i=0; i<3; i++)
for(int j=0; j<3; j++)
ttt[i][j] =' ';
boolean continueFlag = true;
while (continueFlag)
{
displayBoard();
if (gameIsDraw())
{
System.out.println("Game Ends in Draw");
continueFlag = false;
}
else
{
getPlayerInput(currPlayer);
if (winner(currPlayer))
{
System.out.println("We have a winner: " + playerID(currPlayer));
displayBoard();
continueFlag = false;
}
else
{
if (currPlayer == player1) currPlayer = player2;
else currPlayer = player1;
}
}
}
}
public static void main(String[] args)
{
TicTacToe game = new TicTacToe();
String str;
do
{
game.newgame();
System.out.println("Do you want to play Tic-Tac-Toe (y/n)?");
str= game.scan.next();
} while ("y".equals(str));
System.out.println("Bye");
}
}
